The present invention relates generally to a system and method of wood preservation, and in particular to a polymer chemistry system that provides a non-toxic, hydrophobic, elastomeric wood preservative for deterring rot, environmental degradation, termite and mold/fungus attack.
Wood is an economical and renewable building resource. However, untreated wood is subject to attacks by insects, micro-organisms, decay, fungi and environmental weather degradation primarily associated with continuous solar ultraviolet exposure, and long-term cyclic rain, snow and heat exposure. To ensure long-term structural performance, wood must be protected from its natural and environmental predators. Preserved wood is lumber or plywood that has been treated with wood preservatives to protect it from termites and fungal decay. Wood preservation is the process by which wood is preserved. There are a variety of wood preservatives and application methods used, including high pressure impregnation, low pressure and vacuum methods of preservation application, dip treatments and brush or spray-on application methods. Current wood preservation methods are the result of virtually a total focus on the problem of wood preservations and preservatives, with no consideration or evaluation of the long-term consequences of their continued use.
For the past three decades, wood treated with copper, chromium, and arsenic (CCA) has demonstrated unquestionable effectiveness in deterring rot, decay and termite attack. It has become the standard by which to measure the performance and longevity of most wood used for outdoor construction. Today, however, there is an increasingly growing public awareness and concern regarding the negative consequences of the use of toxic heavy metals and environmentally hazardous chemicals in products to which the general public is exposed. These negative aspects have only been observed and determined as a result of long-term use and application.
Federal regulations—notably those of the EPA—list CCA as a wood preservative, but the EPA reached an agreement with lumber companies in February 2002, to phase out its use as a wood preservative in residential/human contact wood products by December 2003. The basis for this phase-out is extensively supported and well established via independent studies by both various government agencies and academic institutions, e.g. EPA, USDA, USPHS, HHS, University of California, Chicago, Alabama, Colorado, to name a few. Collectively, these studies have thoroughly established that CCA is both toxic and a human carcinogen.
On Jul. 11, 2003, a class action lawsuit was filed in federal court claiming that Georgia Pacific Corporation knowingly exposed customers to the toxic human carcinogen known as CCA. Not only is CCA recognized as a toxic human carcinogen, it is now recognized as having a waste disposal problem. Old treated lumber which has dried out, split, warped or twisted during its structural use cannot be disposed of via ordinary methods. It cannot be burned, since the copper, chromium and arsenic parts of CCA produce a lethal variety of toxic gases, which if briefly inhaled by humans of high toxic sensitivity, can cause a variety of serious, if not lethal, neurological disorders of long-term chronic persistence. Although originally considered as anecdotal evidence, occurrences such as livestock dying within one week after being exposed to the downwind gases of burning waste CCA-treated wood, and the cumulative incidences of such events are now regarded as another compelling basis for the classification of CCA as a toxic human carcinogen.
It is an established fact that water-based preservatives continually “leach-out” slowly over extended periods of time. This leaching out is unavoidable since it is a chemistry maxim that water-based solubles will always manifest themselves in their solid crystalline molecular structure form when not in a dissolved state, e.g., Sugar. Leach-out is a direct result of environmental exposure to rain water, melting snow, high humidity, groundwater, and the like. Thus, waste CCA-treated wood cannot be hauled off to a community landfill nor buried, since the toxic CCA will continue to leach out until depleted. The continuous leaching is an excellent vector source for ground water toxic contamination and spreading migration of aquatic toxicity.
Thus, not only is there a need in the art for a system of wood preservation that resists termites and wood decay, as a replacement for the widespread practice of CCA treatment, there is additionally an acute need for a method of containing CCA and similar carcinogens within existing treated lumber and preventing the harmful chemicals from leaching out.
A growing and significant concern about the present use of long-term, persistent toxic hydrocarbons as termicides has resulted in increasing studies on extractives of woods resistant to termites. (Wolcott, 1953; Becker, 1971; Carter, et al., 1978; Jurd and Manners, 1980). Extractives are natural products extraneous to a lignocellulose wall, the cellulose fibers which define the wood's structural fiber composition. They can be removed with inert solvents such as acetone, ethers, and benzene/alcohols. Extractives are from two general sources. The first source are the components involved in a tree's metabolic processes; the second are artifacts resulting from further modification of metabolites by external sources, or means other than a tree's metabolic processes. The knowledge of natural termite resistance of various wood species is important, because either naturally resistant woods or chemically treated susceptible woods are needed in places where wood is exposed to termite attack. The termite resistance of certain wood species results primarily from their organic constituents that are distasteful, repellent or toxic to termites. Although having any or all of these three properties is sufficient to define a relatively effective termicide, a source of reliable and effective extractives is presently viewed as being literally inadequate to meet the demands of today's commercial lumber industry, whose major products are treated Southern Yellow Pine and oak lumber. Thus, there exists a need in the art for a system of wood preservation via present impregnation methods that does not rely on toxic chemicals or termicidal organic wood extractives as a long-term preservative against the devastation caused by termite attacks.
In light of these and other deficiencies in the state of the art, the following objectives of the present invention are enumerated. It should be noted that not all, or necessarily any, of these objectives may be fully met in any given embodiment of the present invention.
It is an objective of the present invention to provide a polymer-based chemistry system for wood preservation and preservatives, which does not contain cooper, chromium, arsenic or other EPA-classified hazardous chemicals.
It is a further objective of the present invention to provide a polymer-based chemistry system for wood preservation and preservatives that is non-toxic to humans.
It is a further objective of the present invention to provide a polymer-based chemistry system for wood preservation and preservatives that is non-carcinogenic to humans.
It is a further objective of the present invention to provide a polymer-based chemistry system for wood preservation and preservatives that is hydrophobic in the cured state.
It is another objective of the present invention to provide a polymer-based chemistry system for wood preservation that is not water-based, for the purpose of eliminating water-based preservative leaching.
It is also an objective of the present invention to provide a polymer-based chemistry system for wood preservation and preservatives that does not depend on solvent-borne non-polymer materials, e.g. paraffins, terpenes, waxes, or linolenes—for the purpose of producing a barrier to water penetration of wood.
It is another objective of the present invention to provide polymer-based chemistry system for wood preservation and preservatives that is inherently termicidal by nullifying termites' ability to digest the lignocellulose fiber construction of wood permeated with impregnation of the system formulations.
It is yet another objective of the present invention to provide a polymer-based chemistry system for wood preservation and preservatives characterized by low viscosity in the applied liquid state in order to facilitate maximum wood impregnation at moderate values of vacuum and pressure, e.g. 15–18 mm vacuum and 25–50 psi pressure.
It is also an objective of the present invention to provide a polymer-based chemistry system for wood preservation that permits a significant reduction in post-impregnation drying time, e.g. from several days to several hours.
It is also an objective of the present invention to provide a polymer-based chemistry system for wood preservation that meets non-hazardous landfill requirements for waste disposal and/or can be buried with no toxic biodegradable results.
It is also an objective of the present invention to provide a polymer-based chemistry system for wood preservation and preservatives that does not adversely respond to solar ultraviolet exposure (approx. 3,600 angstroms). This response characteristic eliminates ultraviolet degradation effects of current preservative methods, such as preservative crystallization, loss of product homogenuity due to structural embrittlement, and continual weather erosion loss of degraded product.
It is also an objective of the present invention to provide a polymer-based chemistry system for wood preservation and preservatives that provides a liquid polymer-based solution for wood impregnation. Immediately upon impregnation, polymerization from the liquid phase to a permanent solid phase is initiated, by virtue of the chemical reactivity of the solution, without requiring, relying on, or modifying external ambient conditions, e.g. temperature, atmospheric pressure, or relative humidity.
It is a further objective of the present invention to provide a polymer-based chemistry system for wood preservation that, when liquid applied via whole-body impregnation or surface penetration methods, is polymerized to a solid-state polyurethane/urea thermoset polymer.
It is yet a further objective of the present invention to provide a polymer-based chemistry system for wood preservation and preservatives that, when applied either as whole-body liquid impregnation or surface penetration, produces a solid-state polyurethane/urea with significant elastomeric properties. Furthermore, an objective of the present invention is an elastomeric property having a % distention-to-yield value of about 450% to 680%, depending on formula composition. The high value of this physical parameter may enable long-term immunity (such as in excess of 10 years) to the degradation effects of weather-related annual thermal stresses associated with shrinking and expansion—as is experienced by non-elastomeric thermoplastic materials.
It is a still further objective of the present invention to provide a polymer-based chemistry system for wood preservation that, when used as a surface penetration, can be applied to damp wood, i.e. wood with a temporary, heavy moisture content acquired from recent prior exposure to rain, snow, or excessive humidity.
It is also an objective of the present invention to provide a polymer-based chemistry system for wood preservation that has no solar ultraviolet exposure-induced objectionable color-tone change, i.e., darkening.
It is also an objective of the present invention to provide a polymer-based chemistry system for wood preservation that enables the inclusion of a wide variety of stains and colorings into the system at the time of system application.
It is also an objective of the present invention to provide a polymer-based chemistry system for wood preservation with a variety of embodiments developed for specific application methods.